The present invention relates to fenders for a relatively stationary offshore platform More particularly, the present invention is directed to a light weight, energy-dissipation bumper system for the columns of an offshore tension leg platform, or the like.
Many sophisticated (and, therefore, expensive) pile protector systems have been devised. Some of these have possible application on offshore platforms such as tension leg platforms, and the like. Among these bumper systems are those shown in U.S. Pat. Nos. 3,503,600 to Rich; 3,541,800 to Walker et al.; 4,032,126 to Laughlin et al.; 4,398,848 to Guilbeau; 4,494,738 to Britton et al.; and 4,650,371 to Sawaragi et al.
Besides being overdesigned and, therefore, not cost effective solutions, a number of these systems would impose undue weight penalties on the floating platform. While not all possible applications for these bumpers are weight sensitive, offshore platforms are particularly susceptible to considerations of weight. Indeed, ss a general rule, for each pound of weight positioned above the waterline, two pounds of structure are required below the waterline to support it. Hence, any bumper system utilized to protect the columns of an offshore platform that does not have weight considerations among its most significant design criteria, will not have satisfactory performance.
The energy-dissipation bumper system of the present invention has two principal design features: (1) light weight, and (2) simplicity, both of which precipitate low cost. First and second coaxial cylindrical shells sandwich a plurality of light-weight crushable tubes. These tubes absorb the energy of a potentially destructive collision solely by being crushed. Tubes which become so damaged as to inadequately protect the column structure to which they are attached can be easily replaced These tubes may either extend radially about the column or axially along the column in a plurality of rows. By preventing ingress of seawater into the bumper system, the hollow crushable tubular members actually provide buoyancy to the platform, as opposed to imposing a weight penalty.
Various other features advantages and characteristics of the present invention will become apparent after a reading of the following detailed description.